Spotting Top-Notch Toms

Since 1863, when Abraham Lincoln first proclaimed the last Thursday of
November an official day for giving thanks, Thanksgiving has been synonymous
with turkeys.

In recent years, other things have almost become icons of the day: football
games, family gatherings, travel, and, of course, leftovers. But while
alterations to the Thanksgiving menu have been relatively minor through the
years, how the traditional main course--turkey--gets to our tables has changed
significantly.

The Pilgrims had to stalk their entree through the wild. Today's production
is considerably more high tech. It has to be, to supply the 4.7 billion pounds
of turkey that U.S. consumers eat every year--a rate of nearly 18 pounds per
person.

Researchers with the Agricultural
Research Service in Beltsville, Maryland--birthplace of the historic
Beltsville Small White turkey--are helping producers keep pace with this demand
and the challenges it poses. At the ARS Germplasm and Gamete Physiology
Laboratory, the focus is on improving the reproductive efficiency of turkeys
and reducing the problems commercial producers face with turkey fertility and
egg production.

A major contributing factor to turkey mating woes is that today's commercial
turkey doesn't look much like its early American counterpart, or even its World
War II-era ancestor. With advances in genetic selection, adult turkey males, or
toms, can weigh up to 85 pounds, whereas a hen weighs around 20 pounds when she
begins to lay eggs. This size difference makes natural mating difficult.

Poultry physiologist Ann Donoghue says that in modern turkey production
virtually all hens are artificially inseminated.(K8096-1)

"We generally have anywhere from 80,000 to 100,000 hens at our hatchery
that are artificially inseminated," says Lynn Bagley, director of
technical services at the Tarhill Turkey Hatchery in Raeford, North Carolina.
"We use thousands of toms to inseminate the hens. We have a few tests to
tell whether or not the semen collected is normal or abnormal, but they're very
labor intensive."

Animal physiologist David P. Froman of Oregon State University originally
developed the test for chickens and, with Donoghue, modified it for use in
studying turkeys.

"Essentially 100 percent of the nearly 300 million turkeys produced
annually in the United States for consumption are the result of artificial
insemination," notes ARS poultry physiologist Ann M. Donoghue, who leads
turkey reproductive studies at the Beltsville lab.

Young turkeys at the Beltsville (Maryland) Agricultural Research Center.
(K8099-3)

Given the importance of artificial insemination to turkey production, a
modern grower might be forgiven for thinking such research achievements
overshadow even development of the Beltsville Small White.

A Breakthrough Six Decades Ago

In the 1930s, Beltsville-based researchers William Burrows and Joseph Quinn
reported groundbreaking methods for semen collection and artificial
insemination for poultry. Those methods are still used today, with a few
modifications.

"Artificial insemination in the turkey industry is a very
well-established practice," Donoghue says.

"Yet the potential for using this method to select toms that can
produce offspring has not been realized. As for managing fertility, there is no
test for evaluating semen quickly that is practical for routine use on
commercial farms and correlates reliably with fertility."

In another advance, in the 1970s, physiologist Thomas J. Sexton developed
the Beltsville Poultry Semen Extender--asolution that dilutes
and preserves the sperm outside of the bird's body--that is sold by commercial
companies and used worldwide. Sexton is now director of the Beltsville
Agricultural Research Center's Livestock and Poultry Sciences Institute.

Development of the Beltsville Poultry Semen Extender allowed turkey semen to
remain viable for up to 24 hours after collection.(K8097-1)

Donoghue says artificial insemination of turkeys is considerably more
efficient than natural mating, given the sheer number of hens that need to be
inseminated. Another plus: With artificial insemination, fewer toms are needed
to keep hens producing fertile eggs. Donoghue says the necessary ratio of toms
to hens decreases from 1 to 10 with natural mating to 1 to 30 with artificial
insemination.

Unlike other production animal systems--dairy cattle, for instance--where
artificial insemination is well established, evaluation of individual males in
the turkey industry is limited to visual checks of semen color, volume, and
concentration of sperm--if evaluation is done at all. The ability to accurately
pinpoint sire potential would have tremendous benefits in improved breeding
efficiency of turkeys.

"The basis of this test isn't anything new, but we used old ideas in a
new way to study the motility of sperm cell populations," says Donoghue.

"Based on studies on turkeys, we found the new information can be used
to identify males that are very fertile--or not," she says.

"In the past, most--if not all--semen evaluation tests have been much
more effective at picking losers rather than winners. This test does
both."

The test could improve the efficiency of picking the best toms, resulting in
more fertile eggs with fewer sires. Donoghue and colleagues, with the support
of the U.S. Egg and Poultry Association, are planning to take the test to the
field for trials in cooperation with the turkey industry.

Since artificial insemination typically involves collecting semen from all
toms in a breeder flock, a readily detectable sperm trait strongly associated
with fertility could be incorporated into breeder tom management fairly easily.
The new sperm motility test is inexpensive, quick, and objective. It requires
minimal knowledge or training to perform and could easily be adapted for
commercial farm use, according to Donoghue.

Microscopic examination will enable physiologist Laura King to see if a freshly
laid egg was fertilized. Any holes made by sperm will show up in a section
(stained for viewing) taken from the surface layer surrounding the yolk in the
area just over the germinal disc.(K8092-1)

"Males with the trait for fast-moving sperm carry that trait through
time," she points out. "If the tom is good today, he'll be good
tomorrow."

In addition to being able to classify toms as winners or losers, it is also
important to understand why and how their sperm differ. By understanding which
physiological characteristics influence fertility, sperm from toms classified
as losers could potentially be improved.

See How They Swim

Using a computer-assisted sperm analysis system (CASA), Donoghue and
colleagues have expanded the knowledge of motility characteristics from
different toms' sperm.

CASA tracks and records information as the sperm move across a microscope
field. Using a computer to capture the data, several hundred sperm tracks from
an individual tom can be analyzed. Scientists in Donoghue's lab have evaluated
hundreds of toms using the sperm motility test and CASA.

Large White turkey male.(K8098-2)

They found that sperm velocity parameters were consistently higher for toms
ranked high by the motility test than for toms ranked lower. These parameters
are a way of measuring how fast and in what direction the sperm are moving.
Studies are in progress to learn why sperm differ in these characteristics.

The scientists are also trying to determine if additives to sperm--such as
caffeine, which has been shown to influence sperm motility in other
species--affect sperm from turkeys classified as winners and losers
differently.

"Sperm from up to 10 to 15 males are usually pooled for artificial
insemination into hens," says Donoghue. "It is generally assumed that
sperm from all toms are going to produce similar numbers of offspring, but this
is not always the case. Some toms may produce offspring and some may not. So
from an economical and practical standpoint, knowing which males' sperm can
fertilize eggs and produce offspring is important."

Donoghue, in collaboration with Tuskegee University scientist Edward J.
Smith in Alabama and ARS poultry physiologist Murray R. Bakst in Beltsville,
inseminated hens with semen from multiple toms and then used DNA fingerprinting
to determine the paternity of the offspring. The results were surprising,
Donoghue reports.

Large White turkey female.(K7043-16)

"When semen from 7 to 10 toms was pooled, we found that only 1 or 2
males produced a majority of the offspring," she notes.

Donoghue says it is possible that sperm motility influences the number of
sperm that make it to the sperm storage tubules in the hen and subsequently
fertilize the eggs.

"If our hypothesis proves correct," she adds, "the sperm
motility test could be adapted and used by the turkey industry as a simple and
reproducible objective method for evaluating the male component of fertility.

Fertile turkey eggs produced at the ARS Germplasm Physiology Laboratory in
Beltsville bear hen identification numbers and the date when each was laid.
(K8095-1)

"The potential impact of sire selection, based on a test that
correlates sperm motility with fertilizing potential, could alter the way
breeder toms are managed throughout the United States," she continues.
"Simply by sorting out males that are not contributing to offspring
production, we estimate a savings of $5 million annually for turkey
breeders."

"We generally inseminate each hen with 200-300 million sperm a
week," notes Tarhill's Lynn Bageley. "Most of the sperm are pooled
from a flock. If we could have a practical way to sort good toms from bad toms,
that could mean very big savings. We would be able to reduce the semen dosages
to the hens, and it would ultimately cut down on the number of toms we need to
maintain to keep our hens in production.

"We're looking forward to any new improvements in the turkey production
process."--By Tara Weaver,
Agricultural Research Service Information Staff.